Two great examples in my opinion of the pros and cons of getting players into professional setups early.
1. Jordan Petaia - I would have loved to see him get the Grealy treatment and put a couple of consistent club years under his belt, have a couple of games where he gets bashed a bit by adults but is still good enough to standout. He has clearly needed time to grow into his body and evolve from the schoolboy player who could score at will, to someone who actually needs to develop a skillset and think about his game. I think Petaia is playing the best footy of his career right now, but it's taken him 5 years of playing professionally and many injuries to get to this point.
2. Samu Kerevi - I watched Kerevi come through the QPR Colts system and 1st Grade at GPS. He played Premier Colts and then GPS 1st grade from 2012 -2014. He also had the benefit of a couple of NRC seasons to hone his skills in a semi-professional environment. One thing you'll notice about Kerevi is he's been able to be the best player on the field at each level he's gone to, from the moment the Reds said 'okay let this bloke play' he was able to get over the gain line and dominate. Now he's probably the only Wallaby who's truly a 'world class player'.
This is the Australian way of selection and it starts very early:
1st XV Level - handful of younger superstars selected over the older equivalent to help grow depth for the following years the bench players are generally younger players as well.
QLD School Boys, Red U18, AUS School Boys, AUS 20s, Super Rugby, International Level - handful of younger superstars selected the older player equivalent would miss out on selection.
QPR do the same - you see a lot of up-and-coming Colts start over 2nd Grade players, generally speaking Premier Colts would be more widely used oppose to a 2nd Grade player. Not always but more often than not.